Why aren't my inputs diplays to my listbox in C#?

using System;
using System.Windows.Forms;

namespace MajorProject1_2
{
    public partial class Form1 : Form
    {
        private double totalLoan;
        private double mounthsCounter;
        private string formatstring;
        private object accumulate1;
        private object accumulate2;
        private int months;
        private object answer;

        public double TotalInterest { get; private set; }
        public double TotalPP { get; private set; }
        public object Value { get; private set; }

        public Form1()
        {
            InitializeComponent();
        }

        private void label1_Click(object sender, EventArgs e)
        {

        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            // select all of the Loan Amount textbox values when the user tabs up
            // use the keypress event to disallow anything but digits, control characters, and the period 

        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void radioButton1_CheckedChanged(object sender, EventArgs e)
        {

        }

        private void label4_Click(object sender, EventArgs e)
        {

        }

        private void label5_Click(object sender, EventArgs e)
        {

        }

        private void button2_Click(object sender, EventArgs e)
        {
            // accumulate the amount of all loans in a variable to later diplay in total loans label 
            accumulate1 = Value;
            accumulate2 = Value;

            // clear the list box 
             listBox1.Items.Clear();

            // clear all of the textboxes and combo box

            textBox1.Clear();
            comboBox2.Items.Clear();
            // set the rebate checkbox.checked property to false 
            checkBox1.Checked = false;
            // set the month 6 radio button as checked 
            if (radioButton1.Checked)
               months = 6;
            // disable the rebate textbox 
            textBox2.Enabled = false;
            // set the focus on the loan textbox 
            textBox1.Focus();








        }

        private void textBox2_TextChanged(object sender, EventArgs e)
        {

        }

        private void radioButton1_CheckedChanged_1(object sender, EventArgs e)
        {

        }

        private void button1_Click(object sender, EventArgs e)
        {


            //declare variables 
            double loan, rate, rebate, months, principalPayment, interest, pmt;
                 
            try
            {
                double.TryParse(textBox1.Text, out loan);
                rate = Convert.ToDouble(comboBox2.Text);
                double.TryParse(textBox2.Text, out rebate);
                if (radioButton1.Checked)
                    months = 6;
                if (radioButton2.Checked)
                    months = 12;
                if (radioButton3.Checked)
                    months = 18;
                if (radioButton4.Checked)
                    months = 24;
                

            }
            catch {
                MessageBox.Show("Please select one from the box!", "Error Message",
                MessageBoxButtons.RetryCancel, MessageBoxIcon.Error);
                groupBox1.Focus();
            }
            // get the intry from loan amount text box 
            double.TryParse(textBox1.Text, out loan);
            // code to read the APR value from the combo box and store it in the variable rate 
            rate = Convert.ToDouble(comboBox2.Text);
            // check for 0 values and run a message telling someone to put the correct input in 
            if (loan == 0)
            {
                MessageBox.Show("Please enter loan amount and annual APR.", "Error Message",
                    MessageBoxButtons.RetryCancel, MessageBoxIcon.Error);
                textBox1.Focus();
            }
            if (rate == 0)
                MessageBox.Show("Please enter loan amount and annual APR.", "Error Message",
                       MessageBoxButtons.RetryCancel, MessageBoxIcon.Error);
            comboBox2.Focus();

            // use the checked method with the rebate checkbox and conditional logic
            if (checkBox1.Checked)
                double.TryParse(textBox2.Text, out rebate);


            //subtract the rebate amount from the loan amount 
            rebate = 0;
            loan = loan - rebate; 
            
            // convert the rate variable from a percent to a decimal (divide by 100) 
            rate = rate / 100;
            //calculate the principal payment amount using the following formula 
            months = 0; 

            principalPayment = rate / 12 * (loan + 0 * Math.Pow(1 + rate / 12, months)) / ((Math.Pow(1 + rate /
            12, months) - 1) * (1 + rate / 12 * 0));
            // calculate the monthly interest amount each month 
            interest = loan * rate / 12;
            // use this code to format the five columns in your listbox 
            string formatString = "{0,5}{1,12}{2,12}{3,12}{4,12}";


            // use a four loop to calculate the amortization schedule for the loan 
            
            //declare monthsCounter 
            for (int monthsCounter = 1; mounthsCounter <= months; monthsCounter = monthsCounter + 1)
            {
                pmt = principalPayment + interest;
                loan = principalPayment - loan - rebate;
                listBox1.Items.Add(String.Format(formatString, monthsCounter, interest.ToString("C"), principalPayment.ToString("N"), pmt.ToString("N"), loan.ToString("N")));

                totalLoan += loan;
                TotalInterest += interest;
                TotalPP += principalPayment;

                interest = loan * rate / 12;
                principalPayment = pmt - interest;

               
            }
            
            listBox1.Items.Add("{0,5}{1,12}{2,12}{3,12}{4,12}");
            listBox1.Items.Add(String.Format(formatString, interest.ToString("C"), principalPayment.ToString("N"), loan.ToString("N")));
            
            
            {

                listBox1.Items.Add("");
                listBox1.Items.Add(String.Format(formatString, interest.ToString("C"), principalPayment.ToString("N"), loan.ToString("N")));


            }

           





        }
       

        
        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)
        {
            // select all of the Loan Amount textbox values when the user tabs up; 
            comboBox2.SelectAll(); 
        }

        private void listBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            // clear listbox if user makes any changes;         
            //listBox1.Items.Clear();
            
        }

        private void button4_Click(object sender, EventArgs e)
        {

            const string message = "Are you sure you want to exit?";
            const string caption = "Exit"; 
            var result = MessageBox.Show(message, caption, MessageBoxButtons.YesNo, MessageBoxIcon.Question);
            if (result == DialogResult.Yes)
            {
                Application.Exit(); 
            }
            else if (result == DialogResult.Yes)
            {
                this.Close();
            }




        }

        private void textBox2_TextChanged_1(object sender, EventArgs e)
        {

        }

        private void radioButton3_CheckedChanged(object sender, EventArgs e)
        {

        }

        private void radioButton2_CheckedChanged(object sender, EventArgs e)
        {

        }

        private void groupBox1_Enter(object sender, EventArgs e)
        {

        }

        private void checkBox1_CheckedChanged(object sender, EventArgs e)
        {

        }

        private void label9_Click(object sender, EventArgs e)
        {

        }

        private void button3_Click(object sender, EventArgs e)
        {
            // write the amount of all loans (stored in a variable) total loans 
            double accumulate1 = double.Parse(textBox3.Text);

            // write the amount of all interest (store in variable) total interest 
            double accumulate2 = double.Parse(textBox4.Text);


        }

        private void textBox4_TextChanged(object sender, EventArgs e)
        {

        }

        private void textBox3_TextChanged(object sender, EventArgs e)
        {

        }
    }
}